Foam used in attics and crawl-spaces must be covered by a thermal barrier.
Building codes regulate the use of most materials used in construction, with state authorities enforcing the codes locally. The International Building Code and the International Residential Code, both of which are established by the International Code Council, govern residential and commercial building activities in the 50 states and the District of Columbia. Chapter 26 of the IBC provides the codes applicable to foam products used in construction, including polyurethane, expanded polystyrene and polyisocyanurate. Fire resistance has the highest priority.
Regulations
The codes specifically regulate the use of foam substances in locations such as residential roofs and crawl spaces. Manufacturers work with the Spray Polyurethane Foam Alliance industry group to develop acceptance criteria for use by the ICC. One result of this collaboration is the provision for builders to satisfy the code using alternate means, as long as this satisfies the fire, durability and other requirements adequately.
Testing Standards
The codes prescribe the standard testing methods that inspectors use in construction to determine compliance and approval. Specific methods of testing used to determine that the products meet minimum criteria include two fire tests, a uniformity of application test and the use of ignition barriers. The performance of the foam is required to be uniform when applied to all surfaces, particularly in attics and crawlspaces. The product must adhere equally to both walls and ceiling surfaces in equal quantities and thicknesses.
Fire Resistance
Foam plastics used in construction must have a protective thermal barrier. If used on the exterior, spray foam must pass roof-covering fire tests. The barrier must comply with the ICC evaluation service's requirement to separate the substance from the building's interior. Specifications for the barrier include half-inch thick gypsum drywall or any other covering that prevents the foam from increasing in temperatures beyond 250 degrees Fahrenheit for a 15-minute period. Foam may be used without a thermal barrier if it passes one of several ICC-approved tests.
Performance
The performance of spray foam is tested using a modified methodology called NFPA 286 that has four levels of acceptance. The first level is based on the time it takes for the foam to reach a maximum heat release rate of 1 megawatt. The second level is the amount of time it takes for the floor to reach a maximum heat flux of 20 kilowatts per square meter. The third level is the time it takes for the upper layer temperature to reach a heat of 1,112 F, and the fourth is the time it takes for the flames to reach the doorway of the testing room.
R-Values and Venting
Prescribed R-values in wall assemblies are R-13 in some regions and R-19 in others. The National Association of Home Builders vetoed attempts to raise the prescribed R-values, saying that the proposed levels were not cost effective. The code permits the installation of spray foam in unvented attics and cathedral ceilings. Studies conducted by the Spray Polyurethane Foam Alliance demonstrated that moisture control was better in buildings that did not have vents, so attempts to amend this provision failed.
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